Generally speaking, the more automated a conveyor system, a storage system, or a transportation system is, the more sophisticated the control mechanisms and telemetric devices must be. One such system is a conventional automobile parking tower which has been in public operation since the early 1970's. This parking tower is disclosed in a number of United States patents by Lichti and Lichti et al, such as U.S. Pat. No. 3,656,608 (incorporated herein by reference). Such a parking tower has a number of items which must be constantly checked to ensure the safe operation of the tower. Among these items to be checked are the absence of any people in the tower area when the conveyor is operated; detection of the entering or exiting of a vehicle; detection or a properly positioned vehicle on a conveyor pan; and detection of any vehicle doors that were left open. The aforementioned conventional parking tower also disclosed in the Lichti et al patents utilizes two mechanical sweeping arms for sweeping close to the sides of a vehicle in a pan located at the tower entrance to determine if a vehicle door were left open. Upon the striking of a vehicle door, the arm activates a microswitch, which in turn provides a signal to indicate an open door and to stop the operation of the parking tower.
Other patents disclose other means for detecting the presence of a vehicle in a conveyor pan or the presence of people in the protected area. Thus, the Inuzuka et al U.S. Pat. No. 3,323,617 (incorporated herein by reference) discloses the use of three photoelectric detecting means located at the entrance and exit to the parking tower for determing the entering, the presence, or the exiting of a vehicle on a conveyor pan. An electrical signal circuit using a plurality of microswitches and electrical storage means (latching relays) is depicted for keeping track of which parking cages are empty and which are full.
The United States Patent to Cheal et al, U.S. Pat. No. 3,877,002 discloses an intrusion detecting system that uses a microwave transmitter and receiver for irradiating microwave energy in a predetermined beam pattern having a unique amplitude modulation and for receiving a signal when the beam is interrupted. Whenever the beam is detected as being interrupted, the device provides an output signal to an alarm. By providing a modulated signal, a plurality of microwave units can be used at the same time without mutual interference.
A system for detecting the presence, the leaving, or the entering of people is disclosed in the patent to Muncheryran, U.S. Pat. No. 3,898,639. The system disclosed in this patent utilizes four laser beams projected on different sides of a wall or fence and the interruption of a particular beam determines whether an individual is attempting to enter or leave the walled area.
The patent to Schwarz U.S. Pat. No. 3,130,298 discloses an electrical circuit and switches for counting a number of vehicles entering and leaving different parking areas of a parking garage. The Cheal et al, Muncheryan and Schwarz patents are incorporated herein by reference.
However, none of the aforementioned systems disclose any means for distinguishing between people and automobiles, for monitoring and controlling the operation, automatically, of a storage conveyor, and which can also determine the undesirable presence of persons within the conveyor operating area.